(1) Field of the Invention
The present invention relates to an improved segmented polyether-ester amide and a process for the preparation thereof. More particularly, the present invention relates to a segmented, colorless polyether-ester amide having a high degree of polymerization, which is obtained by using an aminocarboxylic acid, a poly(alkylene oxide) glycol and a dicarboxylic acid as the main starting materials, and a process for the preparation thereof.
(2) Description of the Prior Art:
Polyether-ester amides are known, and it also is known that polyether-ester amides have excellent impact resistance and elasticity just like polyether-esters and polyether-amides. However, polyether-ester amides contain in the main chain ester units which readily undergo hydrolysis and have a small equilibrium constant of polymerization (the equilibrium constant is ordinarily smaller than 1 and hence the speed of depolymerization is higher) and amide units which tend to cyclize under high vacuum because of thermal equilibrium and to dissociate and evaporate from the system and therefore often cause changes in the copolymerization ratio. Accordingly, to obtain a polymer having a high degree of polymerization, the copolymerization ratio and polymerization conditions are limited and they should be selected within narrow ranges. Furthermore, in polymers of the polyester amide type having ester units and amide units, there is a disadvantage in that a certain decomposition takes place concurrently with the intended polymerization reaction and the polymer is colored.
As the means for eliminating these drawbacks, there have been proposed improved polymerization processes for the preparation of polyether-ester amides. For example, there can be mentioned polymerization processes for the preparation of polyether-ester amides such as as those, disclosed in U.S. Pat. No. 4,230,838, U.S. Pat. No. 4,207,410 and Japanese Patent Application Laid-Open No. 47430/81. According to these processes, however, it is difficult to prepare uncolored polyether-ester amides having a high degree of polymerization industrially.